How does Bioremediation work?

Bioremediation technology exploits various naturally occurring mitigation processes: natural attenuation, biostimulation, and bioaugmentation.

Bioremediation which occurs without human intervention other than monitoring is often called natural attenuation. This natural attenuation relies on natural conditions and behavior of soil microorganisms that are native to soil.

Biostimulation also utilizes native microbial populations to remediate contaminated soils. Biostimulation consists of adding nutrients and other substances to soil to speed up natural attenuation processes.
Bioaugmentation involves introduction of exogenic microorganisms (sourced from outside the soil environment) capable of detoxifying a particular contaminant, sometimes employing genetically altered microorganisms.

During bioremediation, microbes use chemical contaminants in the soil as an energy source and, through oxidation-reduction reactions, metabolize the target contaminant into useable energy for microbes. By-products (metabolites) released back into the environment are typically in a less toxic form than the primary contaminants.

For example, petroleum hydrocarbons can be degraded by microorganisms in the presence of oxygen through aerobic respiration. The hydrocarbon loses electrons and is oxidized while oxygen gains electrons and is reduced. The result is formation of carbon dioxide and water.

Three primary ingredients for bioremediation are:

1) Presence of a contaminant

2) An electron acceptor

3) Presence of microorganisms that are capable of degrading the specific contaminant.

Generally, a contaminant is degraded easily if it is a naturally occurring compound in the environment, or chemically similar to a naturally occurring compound, because microorganisms capable of its biodegradation are more likely to grow.